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Toward Plastic Smart Windows: Optimization of Indium Tin Oxide Electrodes for the Synthesis of Electrochromic Devices on Polycarbonate Substrates
journal contribution
posted on 2016-03-08, 00:00 authored by Marco Laurenti, Stefano Bianco, Micaela Castellino, Nadia Garino, Alessandro Virga, Candido
F. Pirri, Pietro MandracciPlastic
smart windows are becoming one of the key elements in view
of the fabrication of inexpensive, lightweight electrochromic (EC)
devices to be integrated in the new generation of high-energy-efficiency
buildings and automotive applications. However, fabricating electrochromic
devices on polymer substrates requires a reduction of process temperature,
so in this work we focus on the development of a completely room-temperature
deposition process aimed at the preparation of ITO-coated polycarbonate
(PC) structures acting as transparent and conductive plastic supports.
Without providing any substrate heating or surface activation pretreatments
of the polymer, different deposition conditions are used for growing
indium tin oxide (ITO) thin films by the radiofrequency magnetron
sputtering technique. According to the characterization results, the
set of optimal deposition parameters is selected to deposit ITO electrodes
having high optical transmittance in the visible range (∼90%)
together with low sheet resistance (∼8 ohm/sq). The as-prepared
ITO/PC structures are then successfully tested as conductive supports
for the fabrication of plastic smart windows. To this purpose, tungsten
trioxide thin films are deposited by the reactive sputtering technique
on the ITO/PC structures, and the resulting single electrode EC devices
are characterized by chronoamperometric experiments and cyclic voltammetry.
The fast switching response between colored and bleached states, together
with the stability and reversibility of their electrochromic behavior
after several cycling tests, are considered to be representative of
the high quality of the EC film but especially of the ITO electrode.
Indeed, even if no adhesion promoters, additional surface activation
pretreatments, or substrate heating were used to promote the mechanical
adhesion among the electrode and the PC surface, the observed EC response
confirmed that the developed materials can be successfully employed
for the fabrication of lightweight and inexpensive plastic EC devices.